[CF-metadata] Choice of fill value for unpacked data

From: John Caron <caron>
Date: Thu, 11 Oct 2012 14:44:12 -0600

On 10/10/2012 6:36 AM, Jim Biard wrote:
> John,
>
> I agree that there is no ambiguity in the original dataset. I was just
> pointing out a scenario in which the difficulty mentioned by Phil in his
> original post would manifest itself. The methodology referenced by Russ
> won't handle it. If you (for reasons beyond your control) have a packed
> fill value that is inside your valid range, then no guidance is provided
> by CF to automated client software for how to represent the unpacked
> fill value, leaving the user with a requirement to dig back through the
> packed values, find the elements marked as fill, and "manually" mark the
> unpacked values.

Its true CF is silent about this, so "automated client software" has to
make their own Convention. The netcdf-JAVA package supplies a method

   boolean isMissing(double value);

for this purpose. Alternately, it will just set missing real values to
NaNs, which works well in Java. I think NaNs are the right choice for
missing values myself.
Received on Thu Oct 11 2012 - 14:44:12 BST